The present invention relates to an assembling apparatus and method for forming stacks of fuel rods prior to their being loaded into nuclear fuel elements for use in nuclear reactors. More particularly, the invention relates to such an assembling apparatus and method wherein the fuel rods may be received from storage, arranged into stacks which are inspected and selectively transferred to a fuel element loading system under programmed control. The assembling apparatus includes a stacking assembly wherein arrays of side-to-side arranged fuel rods or other cylindrical parts may be rapidly formed into stacks of selected numbers of axially arranged parts suitable for further processing.
Nuclear reactors commonly employ large numbers of fuel rods formed from fissionable material, the fuel rods often being supported in longitudinal passages within a plurality of fuel elements.
In gas-cooled reactors, for example, the reactor core is made up of a plurality of columns of separate fuel elements or blocks. The fuel elements contain a plurality of longitudinal passages which are open at one end. Stacks of axially arranged fuel rods are inserted into each of the longitudinal holes or passages which are adjacent vertical passages for passing a gas coolant through the core. The fuel block may also be commonly provided with additional passages permitting the insertion of control rods as well as grappling devices for raising and lowering the fuel elements in refueling operation.
Due to hazardous radiation, it is necessary to load the fuel rods into the fuel elements by automated or programmed control means in a radiation filtered environment. A number of systems have been devised for this purpose. For example, a copending patent applicaion, Ser. No. 603,531, filed on Aug. 11, 1975 and entitled FUEL ELEMENT LOADING DEVICE, and assigned to the assignee of the present invention, describes a preferred fuel element loading device of a type particularly contemplated for use as an element of the present assembly apparatus.
In order to permit rapid and efficient operation of such loading devices, it is necessary to provide suitable means for transferring the fuel rods from storage and forming them into axially aligned stacks each having a selected number of fuel rods. The actual number of fuel rods within each stack and even the particular fuel blend for the various stacks may vary depending upon the particular application. In addition, it is important that the length of each fuel rod stack be accurately monitored to determine that its length is within close tolerances before being loaded into a longitundinal passage of a fuel element.
The present assembly apparatus also particularly contemplates use of a unit capable of rapidly transferring large numbers of fuel rods, that unit being described in a copending application, Ser. No. 658,391, filed Feb. 17, 1976 and entitled METHOD AND APPARATUS FOR CONTAINER LOADING AND UNLOADING and assigned to the assignee of the present invention.